Method of manufacturing an optical fiber cable

ABSTRACT

An optical fiber cable is provided. The cable includes: an optical fiber core having a central axis; a presser winding covering the optical fiber core; a sheath covering the presser winding; two tension members in the sheath and facing each other with the central axis therebetween; and two rip cords facing each other with the central axis therebetween and being in direct contact with the sheath and the presser winding. The optical fiber core includes a plurality of optical fiber tapes arranged around the central axis and having mutually different stripe ring marks applied thereon. Each optical fiber tapes includes a plurality of optical fibers intermittently adhered to each other.

This is a divisional application based upon U.S. patent application Ser.No. 14/951,750 filed Nov. 25, 2015, the contents of all of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Technical Field

The present invention generally relates to an optical fiber cable and amethod of manufacturing an optical fiber cable.

Description of Related Art

A loose tube cable includes multiple tubes containing an optical fiber,and each tube is filled with a jelly. A slot cable includes a core(slotted core) including multiple slots for housing an optical fiber.

A non-slotted cable does not have any tubes or slotted cores and thusthe outer diameter and the weight of the non-slotted cable can befurther reduced compared with the loose tube cable and the slottedcable. Further, in the non-slotted cable, removal of an optical fiber iseasier than in the loose tube cable which includes a jelly.

However, in the non-slotted cable including single-core optical fibers,identification of the optical fibers may be difficult. On the otherhand, in the non-slotted cable including optical fiber tapes obtained bycollectively coating multiple optical fibers, distortion of the opticalfibers may be significant due to bending of the optical fiber tape.

Relating to the above, Japanese Unexamined Patent Application, FirstPublication No. 2011-221083 describes putting of the same mark onoptical fibers included in an optical fiber tape. PCT InternationalPublication No. WO2015/052951 describes a technique for bunching opticalfiber tape core wires with a bundling material. Japanese UnexaminedPatent Application, First Publication No. 2013-195534 describes anoptical fiber cable in which individual optical fiber tapes are twisted.

SUMMARY

(1) An optical fiber cable according to an aspect of the presentinvention including: an optical fiber core having a central axis; apresser winding covering the optical fiber core; a sheath covering thepresser winding; two tension members in the sheath and facing each otherwith the central axis therebetween; and two rip cords facing each otherwith the central axis therebetween and being in direct contact with thesheath and the presser winding, wherein the optical fiber core includesa plurality of optical fiber tapes arranged around the central axis andhaving mutually different stripe ring marks applied thereon, and eachoptical fiber tapes includes a plurality of optical fibersintermittently adhered to each other.

(2) It may be arranged such that the presser winding and the sheath arein direct contact with each other.

(3) It may be arranged such that the optical fiber core includes aplurality of optical fiber units arranged around the central axis, eachunit includes the optical fiber tapes and the bunching members bunchingthe optical fiber tapes, and the bunching members are capable of beingdifferentiated from each other.

(4) It may be arranged such that each bunching member includes abunching string arranged in a direction of the central axis so as to bewound around the optical fiber tapes.

(5) It may be arranged such that each bunching member includes a firstbunching string and a second bunching string, the first bunching stringand the second bunching string arranged in a direction of the centralaxis so as to be wound around the optical fiber tapes, and the windingdirection of the first bunching string and the winding direction of thesecond bunching string are opposite to each other.

(6) It may be arranged such that each bunching member includes a firstbunching string and a second bunching string, the first bunching stringand the second bunching string arranged in a direction of the centralaxis so as to be wound around the optical fiber tapes, and the windingdirection of the first bunching string and the winding direction of thesecond bunching string are reversed at a point at which the firstbunching string and the second bunching string come into contact witheach other.

(7) It may be arranged such that the optical fiber units are mutuallytwisted in an SZ manner.

(8) It may be arranged such that the optical fiber core includes aplurality of inner units arranged around the central axis and aplurality of outer units arranged around the inner units, each innerunit and each outer unit includes the optical fiber tapes and thebunching members for bunching the optical fiber tapes, and the bunchingmembers are capable of being differentiated from each other.

(9) It may be arranged such that each bunching member includes abunching string arranged in a direction of the central axis so as to bewound around the optical fiber tapes.

(10) It may be arranged such that each bunching member includes a firstbunching string and a second bunching string, the first bunching stringand the second bunching string arranged in a direction of the centralaxis so as to be wound around the optical fiber tapes, and the windingdirection of the first bunching string and the winding direction of thesecond bunching string are opposite to each other.

(11) It may be arranged such that each bunching member includes a firstbunching string and a second bunching string, the first bunching stringand the second bunching string arranged in a direction of the centralaxis so as to be wound around the optical fiber tapes, and the windingdirection of the first bunching string and the winding direction of thesecond bunching string are reversed at a point at which the firstbunching string and the second bunching string come into contact witheach other.

(12) It may be arranged such that the inner units are mutually twistedin an SZ manner, and the outer units are mutually twisted in an SZmanner.

(13) A method of manufacturing an optical fiber cable according to anaspect of the present invention includes: feeding a plurality of opticalfiber tapes including a plurality of optical fibers intermittentlyadhered to each other; forming an optical fiber core by gathering theoptical fiber tapes; covering an outer circumference of the opticalfiber core with a presser winding; and covering an outer circumferenceof the presser winding with a sheath, the feeding of the optical fibertapes, the forming of the optical fiber core, the covering of the outercircumference of the optical fiber core with the presser winding, andthe covering of the outer circumference of the presser winding with thesheath are performed in a tandem manner.

(14) It may be arranged such that the forming of the optical fiber corefurther includes: forming a plurality of optical fiber units by dividingthe optical fiber tapes into multiple groups and bunching each groupusing a bunching member; and mutually twisting the optical fiber unitsin an SZ manner.

(15) It may be arranged such that the forming of the optical fiber corefurther includes: forming a plurality of optical fiber units by dividingthe optical fiber tapes into multiple groups and bunching each groupusing a bunching member; forming an inner core by mutually twisting someof the optical fiber units in an SZ manner; and forming an outer core bymutually twisting the remaining of the optical fiber units in an SZmanner so as to cover an outer circumference of the inner core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross sectional view showing an example of an optical fibercable according to an exemplary embodiment of the present invention.

FIG. 1B is a cross sectional view showing another example of the opticalfiber cable according to an exemplary embodiment of the presentinvention.

FIG. 1C is a cross sectional view showing still another example of theoptical fiber cable according to an exemplary embodiment of the presentinvention.

FIG. 1D is an enlarged view showing part of an optical fiber cable.

FIG. 1E is an enlarged view showing part of an optical fiber cable.

FIG. 2 is a schematic view showing an example of a plurality of opticalfiber tapes on which mutually different marks are applied.

FIG. 3 is a schematic view showing an example of a plurality of theoptical fibers which are intermittently adhered to each other.

FIG. 4 is a perspective view showing an example of a plurality of theoptical fiber tapes which are bunched using a bunching member.

FIG. 5 is a perspective view showing another example of a plurality ofthe optical fiber tapes which are bunched using a bunching member.

FIG. 6 is a perspective view showing still another example of aplurality of the optical fiber tapes which are bunched using a bunchingmember.

FIG. 7A is a side view showing an inner core including inner unitsmutually twisted in an SZ manner.

FIG. 7B is a side view showing an outer core which includes outer unitstwisted together in an SZ manner and covers the inner core.

FIG. 8 is a schematic view showing an example of an apparatus formanufacturing the optical fiber cable according to an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the drawings.

<Optical fiber cable>

FIGS. 1A to 1C are cross sectional views showing an example of the crosssection perpendicular to the longitudinal direction of an optical fibercable according to an exemplary embodiment of the present invention.FIGS. 1D and 1E are an enlarged view showing part of the optical fibercable.

An optical fiber cable 10 includes: an optical fiber core 2 having acentral axis Z; a presser winding 3 covering the optical fiber core 2; asheath 4 covering the presser winding 3; two tension members 5 which arepresent in the sheath 4 and face each other with the central axis Ztherebetween; and two rip cords 6 which face each other with the centralaxis Z therebetween and are in direct contact with the sheath 4 and thepresser winding 3.

The optical fiber core 2 includes a plurality of optical fiber tapes 20which are arranged around the central axis Z. The optical fiber core 2exemplarily shown in FIG. 1A includes three pieces of the optical fibertape 20 arranged around the central axis Z.

The optical fiber core 2 may include a plurality of optical fiber units2 a which are arranged around the central axis Z and each include aplurality of the optical fiber tapes 20. The optical fiber core 2exemplarily shown in FIG. 1B includes three optical fiber units 2 aarranged around the central axis Z (single-layer structure).

The optical fiber core 2 may include a plurality of optical fiber units2 a (inner units) arranged around the central axis Z and a plurality ofoptical fiber units 2 b (outer units) arranged around the inner units 2a. The optical fiber core 2 exemplarily shown in FIG. 1C includes threeinner units 2 a arranged around the central axis Z and nine outer units2 b arranged around the three inner units 2 a (multilayer structure). Inthe optical fiber cable 10 exemplarily shown in FIG. 1C, the three innerunits 2 a configure an inner core 2A, while the nine outer units 2 bconfigure an outer core 2B.

The optical fiber core 2 including a plurality of optical fiber units 2a (2 b) may be either the single-layer structure or the multilayerstructure depending on the number of the optical fiber units. The numberof the optical fiber units 2 a (2 b) may be determined depending on theintended use of the optical fiber cable.

It should be noted that the cross section of the optical fiber core 2may be circular as shown in FIGS. 1A to 1C or elliptical.

In the optical fiber cable 10 exemplarily shown in FIG. 1A, the opticalfiber core 2 includes a plurality of the optical fiber tapes 20 on whichmutually different marks 22 are applied. In the optical fiber cables 10exemplarily shown in FIGS. 1B and 1C, the optical fiber units 2 a (2 b)include a plurality of the optical fiber tapes 20 on which mutuallydifferent marks 22 are applied.

FIG. 2 exemplarily shows five pieces of the optical fiber tape 20 onwhich mutually different marks 22 (stripe ring marks) are applied. Eachpiece of the optical fiber tape 20 includes a plurality of opticalfibers 1 as described in detail below.

The five pieces of the optical fiber tape 20 shown in FIG. 2 can bedifferentiated from each other by the number or thickness of the ringmarks 21, the ring marks 21 configuring the stripe ring marks 22.Therefore, the optical fiber tapes 20 included in the optical fiber core2 can be differentiated from each other. In the optical fiber cable 10in which the optical fiber core 2 includes the optical fiber units 2 a(2 b), the optical fiber tapes 20 included in each optical fiber unitcan be differentiated from each other. Thus, it is possible to specify atarget piece of the optical fiber tape 20 among the optical fiber tapes20.

In the example shown in FIG. 2, a plurality of stripe ring marks 22 areapplied at a pitch Pm in the longitudinal direction of the optical fibertape 20. The pitch Pm may be appropriately determined so that anoperator can see the pitch when removing the optical fiber 1 from theoptical fiber cable 10. The pitch Pm may be determined so as to have aspecific relationship with the pitch of a bunching member 7 describedbelow.

It should be noted that the marks 22 are not limited to stripe ringmarks as shown in FIG. 2, and appropriate marks may be employed. Thenumber of the marks 22 may be determined depending on the number of thepieces of the optical fiber tape 20 included in the optical fiber core 2or each optical fiber unit 2 a or 2 b.

Each piece of the optical fiber tape 20 includes a plurality of opticalfibers 1 which are intermittently adhered to each other. FIG. 3 shows anexample of a piece of the optical fiber tape 20 including twelve opticalfibers 1 which are intermittently adhered to each other with connectionmembers 8.

Between two optical fibers 1 adjacent to each other, a plurality ofconnection members 8 are arranged in the longitudinal direction (Ydirection in FIG. 3) of the optical fiber 1 at certain intervals(intermittently). In the width direction (X direction in FIG. 3) of theoptical fiber tape 20 as well, a plurality of connection members 8 areintermittently arranged. In addition, there is a gap between two opticalfibers 1 adjacent to each other. The optical fiber tape 20 can be bentin a direction perpendicular to the longitudinal direction of theoptical fiber tape at the connection members 8. In other words, theoptical fiber tape 20 can be irreversibly and flexibly transformed atthe connection members 8 and thus is capable of having a planar form asshown in FIG. 3 or a steric form.

Therefore, when a bending stress is applied to the optical fiber cable10, it is possible to prevent the stress from being applied to theoptical fibers 1 in a biased manner. This allows the optical fiber cable10 to have a certain degree of bending resistance without using anytubes or slotted cores.

The number of the optical fibers 1 in a single piece of the opticalfiber tape 20 may be determined depending on the intended use etc. ofthe optical fiber cable 10. For example, a piece of the optical fibertape 20 including four, eight, twelve, or sixteen (multiples of four)optical fibers 1 may be employed. In this case, fusion splicing betweenthe optical fiber cable and an existing optical cable includingmultiples of four optical fibers can be easily performed. Particularly,with the number of the optical fibers 1 being twelve or less, collectivefusion splicing becomes possible using an existing fusion splicerbecause existing fusion splicers are intended to be used for an opticalcable including twelve or less optical fibers.

The optical fiber 1 may be an optical fiber, or an optical fiber tapecore wire having a coating layer on the outer circumference of anoptical fiber.

The optical fibers 1 in a single piece of the optical fiber tape 20 mayhave different colors from each other. In this case, it is possible tospecify a target optical fiber among the optical fibers 1 included inthe single piece of the optical fiber tape 20.

The optical fiber 1 can be colored by, for example, an additionalcolored layer. When using an optical fiber tape core wire, the coatinglayer thereof may be colored.

The presser winding 3 may be wound 1.2 or more times around the opticalfiber core 2 in a cross section thereof. In other words, thecircumferential length of the presser winding 3 may be 1.2 times thecircumference length of the optical fiber core 2 in a cross sectionperpendicular to the central axis Z of the optical fiber core 2. In thiscase, it is possible to prevent the optical fiber core 2 or the opticalfiber units 2 a (2 b) from inadvertently projecting out when the sheath4 in the optical fiber cable 10 is ripped.

Examples of the presser winding 3 include, for example, a piece ofwater-absorbing tape. In this case, intrusion of moisture into theoptical fiber core can be prevented. Additionally, a non-woven fabric,polyester tape, or the like may be used as the presser winding 3. Amaterial for the presser winding 3 may be appropriately determineddepending on the intended purpose.

Examples of the sheath 4 include, for example, a resin such aslow-density polyethylene (LDPE), medium-density polyethylene (MDPE),high-density polyethylene (HDPE), and polyvinyl chloride (PVC).

Examples of the tension member 5 include, for example, a metal wire suchas a high-strength glass fiber, a tensile-strength fiber such as Kevlar,and a steel wire. While the optical fiber cable 10 shown in FIGS. 1A to1C includes two tension members 5, the number of tension members may bemore than two. For example, two sets of the tension members 5 (fourtension members 5 in total) may be respectively arranged at positions atwhich the tension members face each other with the central axis Ztherebetween.

Examples of the rip cord 6 include, for example, a string made of apolyester fiber, an aramid fiber, a glass fiber, or the like. Since therip cord 6 is in contact with the presser winding 3 as exemplarily shownin FIGS. 1D and 1E, the rip cord allows easy access to the optical fibercore 2 covered with the presser winding 3 when the sheath 4 is ripped bythe rip cord 6.

Particularly, even in the optical fiber cable in which the presserwinding 3 and the sheath 4 are not tightly adhered to each other, thesheath 4 can be divided into halves by ripping the sheath 4 using thetwo rip cords 6 which face each other with the central axis Ztherebetween. Therefore, it is possible to improve the workability ofremoving the optical fiber 1 from the optical fiber cable 10.

The rip cord 6 may be in contact with the presser winding 3 and beembedded in the sheath 4 as shown in FIG. 1D. Alternatively, the ripcord 6 may be arranged between the sheath 4 and the presser winding 3 soas to be in contact with the sheath 4 and the presser winding 3 whilehaving gaps g surrounded by the rip cord 6, the sheath 4, and thepresser winding 3 as shown in FIG. 1E. In this case, the sheath 4 can bemore easily ripped using the rip cords 6.

As shown in FIGS. 1A to 1C, the optical fiber cable 10 may include twoprotrusions T that are continuous in the longitudinal direction of theoptical fiber cable 10 on the surface of the sheath 4. Each protrusion Tmay be arranged on substantially an extension of a straight lineconnecting the central axis Z and the rip cord 6. In this case, it ispossible to prevent erroneous peeling of the sheath near the tensionmember 5. For example, the protrusion T is helpful in specifying theangular position of the rip cord 6 in a dark place.

The presser winding 3 and the sheath 4 may be in direct contact witheach other. In this case, it is possible to reduce the outer diameter ofthe optical fiber cable compared with an optical fiber cable includingan additional coarsely wound string between the presser winding 3 andthe sheath 4. It should be noted that the coarsely wound string betweenpresser winding 3 and the sheath 4 can be omitted using a tandemmanufacturing method described below.

The optical fiber unit 2 a (2 b) may further include bunching members 7bunching the optical fiber tapes 20, and the bunching members 7 may bedifferentiated from each other. In this case, the optical fiber units 2a (2 b) can be differentiated from each other.

In the optical fiber core 2 including the optical fiber units 2 a (2 b),when the respective optical fiber units 2 a (2 b) can be differentiatedfrom each other using the bunching members 7, the optical fiber tapes 20can be differentiated from each other using the marks 22, and theoptical fibers 1 can be differentiated from each other using colors, itwill be possible to differentiate all the optical fibers 1 in theoptical fiber cable 10 from each other. In this case, in an operation ofremoving the optical fiber 1 from the optical fiber cable 10, it ispossible to specify a target optical fiber 1 among all the opticalfibers 1 included in the optical fiber core 2.

The bunching member 7 may include a bunching string 7 a arranged in adirection of the central axis Z so as to be wound around the opticalfiber tapes 20. For example, as shown in FIG. 4, the bunching string 7 amay be helically wound around the optical fiber tapes 20 at a pitch Pb.

The bunching member 7 may include a first bunching string 7 b and asecond bunching string 7 c which are arranged in the direction of thecentral axis Z so as to be wound around the optical fiber tapes 20, andthe winding direction of the first bunching string 7 b and the windingdirection of the second bunching string 7 c may be opposite to eachother. For example, as shown in FIG. 5, the first bunching string 7 bmay be helically wound around the optical fiber tapes 20 at a pitch Pb,while the second bunching string 7 c may be helically wound around theoptical fiber tapes 20 at a pitch Pb in a direction opposite to thewinding direction of the first bunching string 7 b.

The bunching member 7 may include a first bunching string 7 d and asecond bunching string 7 e which are arranged in the direction of thecentral axis Z so as to be wound around the optical fiber tapes 20, andthe winding direction of the first bunching string 7 d and the windingdirection of the second bunching string 7 e may be reversed at points 7f at which the first bunching string 7 d and the second bunching string7 e come into contact with each other. For example, as shown in FIG. 6,the winding direction of the first bunching string 7 d may be reversedat the contact points 7 f every half cycle. Similarly, the windingdirection of the second bunching string 7 e may also be reversed atpoints 7 f every half cycle. In FIG. 6, the distance (pitch) between theadjacent contact points 7 f in the longitudinal direction of the opticalfiber tape 20 is shown as Pb.

At the contact point 7 f, the first bunching string 7 d and the secondbunching string 7 e may be connected to each other by thermal fusionbonding, adhesion using an adhesive, or the like.

Disconnection between the first bunching string 7 d and the secondbunching string 7 e at the contact point 7 f by pulling the firstbunching string 7 d and the second bunching string 7 e in oppositedirections will allow easy access to the optical fiber tape 20. Thus, itis possible to improve the workability of removing the optical fiber 1from the optical fiber cable 10.

Alternatively, the first bunching string 7 d may be linearly arrangedalong the longitudinal direction of the optical fiber tape 20 and thesecond bunching string 7 e may be wound around the optical fiber tape 20such that the winding direction of the second bunching string 7 e isreversed at the contact points 7 f every cycle. It may be possible toapply four bunching strings to the optical fiber tape 20 in which thewinding directions of the bunching strings are reversed at contactpoints at which two of the bunching strings come into contact with eachother every quarter cycle. In these cases as well, it is possible tofacilitate access to the optical fiber tape 20.

The pitch Pb for the bunching strings (7 a to 7 e) and the pitch Pm forthe marks 22 may satisfy a relationship of 2Pb≥Pm. When disconnectingand separating the bunching strings over a length of two pitches (2Pb)or more, removal of the optical fiber tape 20 will become easy and themarks 22 will be visually confirmed easily. In other words, ripping ofthe bunching strings over a length of two pitches thereof will make itpossible to improve the workability of removing the optical fiber tape20 and specify a target piece of the optical fiber tape 20 among theoptical fiber tapes 20 bunched together with the bunching strings. Inthe example of FIG. 6, the optical fiber tape 20 is exposed over atwo-pitch period length of the bunching strings by breaking the jointbetween the first bunching string 7 d and the second bunching string 7 eat one contact point 7 f.

Examples of the bunching member 7 (the bunching strings 7 a to 7 e)include, for example, a high-melting-point resin such as polypropylene(PP), polyamide (PA), and polyethylene terephthalate (PET); or alow-melting-point resin such as polyethylene (PE), an ethylene vinylacetate (EVA) copolymer, and an ethylene ethyl acrylate (EEA) copolymer.

The optical fiber units 2 a may be twisted together in an SZ manner.When the optical fiber units 2 a are twisted together in an SZ manner,the optical fiber core 2 in the optical fiber cable 10 as exemplarilyshown in FIG. 1B can be formed.

The respective inner units 2 a may be mutually twisted in an SZ manner,and the outer units 2 b may be mutually twisted in an SZ manner. Forexample, the inner units 2 a configuring the inner core 2A are mutuallytwisted in an SZ manner as shown in FIG.

7A, and further, the outer units 2 b configuring the outer core 2B aremutually twisted in an SZ manner so as to cover the inner core 2A asshown in FIG. 7B. In this way, the optical fiber core 2 in the opticalfiber cable 10 as shown in FIG. 1C may be formed.

It should be noted that the SZ twisting refers to twisting in two ormore elements are twisted alternately with a left-hand twist (S twist)and a right-hand twist (Z twist). In other words, in the SZ twisting,the twisting directions of elements reverse at reverse points.

When twisting the inner units 2 a and the outer units 2 b separately, itwill be possible to reduce the diameter of the entire optical fiber coreand, further, to decrease the twisting angle compared with an opticalfiber core in which all the optical fiber units are twisted together. Asdescribed above, whether all the optical fiber units are twistedtogether or the inner units 2 a and the outer units 2 b are separatelytwisted may be appropriately determined depending on the number of theoptical fiber units 2 a (2 b). It should be noted that the twistingangle refers to an angle at which the optical fiber units 2 a (2 b) aretwisted between two reverse points adjacent to each other.

The SZ twisting will make it possible to easily untwist the mutuallytwisted outer units 2 b at the reverse points in the outer core 2B.Further, it will be possible to untwist the mutually twisted inner units2 a at the reverse points in the inner core 2A inside the outer core 2B.Therefore, it is possible to improve the workability of removing theoptical fiber 1 from the optical fiber cable 10. Even in the opticalfiber cable 10 exemplarily shown in FIG. 1B, in which all the opticalfiber units are SZ-twisted, it is possible to improve the workability ofremoving the optical fiber 1 from the optical fiber cable 10.

<Method of Manufacturing Optical Fiber Cable>

A method of manufacturing the optical fiber cable according to anexemplary embodiment of the present invention includes: feeding theoptical fiber tapes 20 including a plurality of optical fibers 1intermittently adhered to each other; forming the optical fiber core 2by gathering the optical fiber tapes 20; covering the outercircumference of the optical fiber core 2 with the presser winding 3;and covering the outer circumference of the presser winding 3 with thesheath 4.

The feeding of the optical fiber tapes 20, the forming of the opticalfiber core 2, the covering of the outer circumference of the opticalfiber core 2 with the presser winding 3, and the covering of the outercircumference of the presser winding 3 with the sheath 4 are performedin a tandem manner (tandem manufacturing). In other words, the feedingof the optical fiber tapes 20 through the covering of the presserwinding 3 is performed inline.

According to the above-described manufacturing method, since the feedingof the optical fiber tapes 20, the forming of the optical fiber core 2,the covering of the outer circumference of the optical fiber core 2 withthe presser winding 3, and the covering of the outer circumference ofthe presser winding 3 with the sheath 4 are collectively performed, itis possible to suppress the manufacturing cost of the optical fibercable 10.

Particularly, since the covering of the optical fiber core 2 with thepresser winding 3 is performed inline with the covering of the presserwinding 3 with the sheath 4, it is possible to manufacture the opticalfiber cable 10 without performing any coarse winding on the presserwinding 3 using a coarsely wound string. Therefore, it is possible toimprove the manufacturing efficiency of the optical fiber cable 10.Further, it is possible to omit a step of removing coarsely wound stringwhen performing an operation of removing the optical fiber 1 from theoptical fiber cable 10, and thus improve the workability of removing theoptical fiber 1.

The forming of the optical fiber core may further include: forming aplurality of optical fiber units 2 a by dividing the optical fiber tapes20 into multiple groups and bunching each group using the bunchingmembers 7; and mutually twisting the optical fiber units 2 a in an SZmanner. In this case, particularly in the manufacturing of the opticalfiber cable 10 including the optical fiber units 2 a as exemplarilyshown in FIG. 1B, it is possible to perform the mutual twisting of theoptical fiber units 2 a in an SZ manner inline with the other steps, andthus suppress the manufacturing cost of the optical fiber cable.

The forming of the optical fiber core may further include: forming aplurality of optical fiber units 2 a and 2 b by dividing the opticalfiber tapes 20 into multiple groups and bunching each group using thebunching members 7; forming an inner core 2A by mutually twisting someof the optical fiber units 2 a in an SZ manner; and forming an outercore 2B by mutually twisting the remaining units 2 b in an SZ manner soas to cover the outer circumference of the inner core 2A. In this case,particularly in the manufacturing of the optical fiber cable 10including the optical fiber units 2 a and 2 b as exemplarily shown inFIG. 1C, it is possible to perform the forming of the inner core 2A theforming of the outer core 2B inline with the other steps, and thussuppress the manufacturing cost of the optical fiber cable.

FIG. 8 is a schematic view exemplarily showing an apparatus 30 formanufacturing the optical fiber cable 10. Further detail of the methodof manufacturing the optical fiber cable according to the presentembodiment will be described with reference to FIG. 8. In the followingdescription, the manufacturing of the optical fiber cable 10 includingthe inner units 2 a and the outer units 2 b, as exemplarily shown inFIG. 1C, will be mainly described. In the manufacturing of the opticalfiber cable 10 as exemplarily shown in FIGS. 1A and 1B, some of stepsdescribed below may be appropriately removed.

The apparatus 30 includes: a feeder 40 for feeding a plurality ofoptical fiber tape 20; a bunching section 50 for forming a plurality ofoptical fiber units 2 a and 2 b by bunching the pieces of the opticalfiber tape 20 using the bunching members 7; a twisting section 60 forforming an inner core 2A by mutually twisting some of the optical fiberunits 2 a in an SZ manner and forming an outer core 2B by mutuallytwisting the remaining units 2 b in an SZ manner so as to cover theouter circumference of the inner core 2A; a presser winding section 70for covering the outer circumference of the outer core 2B with thepresser winding 3; a sheath section 80 for covering the outercircumference of the presser winding 3 with the sheath 4; a conveyancecaterpillar 90; and a winding section 91 for winding the optical fibercable 10.

The feeding section 40 includes a plurality of reels 41 around which theoptical fiber tape 20 is wound. The optical fiber tapes 20 fed from thereels 41 are divided into a desired number of optical fiber tape 20groups, and each group of the optical fiber tapes 20 is bunched usingthe bunching member 7 in the bunching section 50, thereby producing aplurality of optical fiber units 2 a (2 b). Each group of the opticalfiber tapes 20 may be bunched, for example, using the bunching member 7as shown in FIGS. 4 to 6. It should be noted that, in the manufacturingof the optical fiber cable 10 as exemplarily shown in FIG. 1A, bunchingof the optical fiber tapes using the bunching members may be omitted.

The twisting section 60 includes a plurality of round-shape linedistribution boards 61. The line distribution boards 61 have multipleholes arranged in the circumferential direction thereof, and one of theoptical fiber units 2 a (2 b) obtained in the bunching section 50 iscapable of passing through the hole. A line distribution board 61through which the inner layer unit 2 a passes and another linedistribution board 61 through which the outer layer unit 2 b passes areseparately provided, and mutual SZ twisting of the inner units 2 a andthe mutual SZ twisting of the outer units 2 b can be performed byturning the respective line distribution boards 61. The outercircumference of the inner core 2A obtained by mutually twisting theinner units 2 a in an SZ manner is covered with the outer core 2Bobtained by mutually twisting the outer units 2 b in an SZ manner,thereby producing the optical fiber core 2.

It should be noted that, in the manufacturing of the optical fiber cable10 as exemplarily shown in FIG. 1A, there is no need for twisting, andthus the twisting may be omitted. In the manufacturing of the opticalfiber cable 10 as exemplarily shown in FIG. 1B, since there are no outerunits 2 b, only the SZ twisting of the optical fiber units 2 a may beperformed.

The presser winding section 70 includes two reels 71 around which thetension member 5 is wound and a reel 72 around which the presser winding3 is wound. The outer circumference of the optical fiber core 2 obtainedin the twisting section 60 is covered with the presser winding 3 fedfrom the reel 72. Two tension members 5 fed from the reels 71 arearranged on or above the outer circumference of the presser winding 3along the longitudinal direction.

The sheath section 80 includes an extruder 81 and a cooling device 82.The optical fiber core 2 covered with the presser winding 3 and the twotension members 5 attached thereto in the longitudinal direction arecovered with a molten resin (the raw material of the sheath 4) extrudedfrom the extruder 81. The molten resin is solidified in the coolingdevice 82 and thus the sheath 4 including two tension members 5 isformed on the outer circumference of the presser winding 3, therebyproducing an optical fiber cable 10. The optical fiber cable 10 passesthrough the conveyance caterpillar 90 and is wound in the windingsection 91.

The conveyance caterpillar 90 gives a tensile strength to the opticalfiber cable 10 in the longitudinal direction (the flow direction of themanufacturing line) and enables the flow from the feeding of the opticalfiber tape 20 in the feeding section 40 through the imparting of thesheath in the sheath section 80.

Some exemplary embodiments of the present invention have been describedabove, but these embodiments are simply examples of the presentinvention and do not limit the present invention. Any addition, removal,and substitution of components and modification of the present inventionare allowed within the scope of the present invention. Therefore, thepresent invention is not limited by the above description and is onlylimited by the scope of the claims.

What is claimed is:
 1. A method of manufacturing an optical fiber cable, the method comprising: feeding a plurality of optical fiber tapes comprising a plurality of optical fibers intermittently adhered to each other; forming an optical fiber core by gathering the optical fiber tapes; covering an outer circumference of the optical fiber core with a presser winding; and covering an outer circumference of the presser winding with a sheath, wherein the feeding of the optical fiber tapes, the forming of the optical fiber core, the covering of the outer circumference of the optical fiber core with the presser winding, and the covering of the outer circumference of the presser winding with the sheath are performed in a tandem manner, and wherein the forming of the optical fiber core further comprises forming a plurality of optical fiber units, each optical fiber unit comprising the optical fiber tapes.
 2. The method of manufacturing an optical fiber cable according to claim 1, wherein the optical fiber units are formed by dividing the optical fiber tapes onto multiple groups and bunching each group using a bunching member.
 3. The method of manufacturing an optical fiber cable according to claim 1, wherein the forming of the optical fiber core further comprises: forming a plurality of optical fiber units by dividing the optical fiber tapes into multiple groups and bunching each group using a bunching member; forming an inner core by mutually twisting some of the optical fiber units in an SZ manner; and forming an outer core by mutually twisting the remaining of the optical fiber units in an SZ manner so as to cover an outer circumference of the inner core.
 4. The method of manufacturing an optical fiber cable according to claim 1, wherein the forming of the optical fiber core further comprises mutually twisting the optical fiber units in an SZ manner.
 5. The method of manufacturing an optical fiber cable according to claim 1, wherein the covering of the outer circumference of the presser winding with the sheath are performed in an extruder, and wherein the forming of the optical fiber core further comprising gathering and mutually twisting the optical fiber units immediately before entering the extruder.
 6. The method of manufacturing an optical fiber cable according to claim 1, wherein the covering of the outer circumference of the presser winding with the sheath are performed in an extruder, and wherein the covering of the outer circumference of the optical fiber core with the presser winding is performed immediately before the entering the extruder. 